Recent Courses

Research Interests

The organisms

The coccolithophorid algae are calcifying members of the Haptophyta (Prymnesiophyceae). They are the only known organisms that can calcify (calcium carbonate) subcellularly and who exercise precise control over the shape of their calcified scales (coccoliths) which are exocytosed to form an external cell cover (coccosphere). More than a hundred species of coccolithophorids have been described with each species displaying unique shape and size of crystallized coccoliths.

Significance

Members of the group have a world-wide distribution and are frequently found at high abundances in the sub-polar oceans. Their evolutionary history extends back to the Jurassic which makes them useful fossils for stratigraphic analyses and oil exploration.

The coccolithophorids draw down CO2 and bicarbonate from the ocean/atmospheric pools and contribute to carbonate archives in deep sea sediments. Thus coccolithophorid calcification is an important link in the global carbon cycle.

The coccolithophores have exciting potential for advances in nano-fabrication. The genetics, assembly and morphogenesis of the coccoliths (organo-crystalline composites) are under the direct control of the organism and remain virtually unexplored by modern tools.

Laboratory Studies

We have introduced Pleurochrysis for biochemical and molecular studies of calcification. Both Pleurochrysis and Emiliania huxleyi offer opportunities for an experimental approach that complements and extends the oceanographic and ecophysiological observations that have preceded our work.

Our interests lie along the following lines:

Carbon concentrating mechanisms. An understanding of the biochemistry and cell biology of the coccolith vesicle; its membrane ion transporters and their relationship to carbon utilization in the chloroplast will lead to more robust predictions for change in the global carbon cycle and, potentially, climate. Other studies will focus on the regulation of expression, and cellular localization of carbonic anhydrases as organisms experience greater or lesser alkalinity, CO2, salinity, and temperature with the goal of understanding how these parameters may influence coccolithophore calcification.

Coccolith Vesicle proton pump. The coccolith vesicle membrane exhibits proton-pumping activity and, along with the Golgi, is the localization of the vacuolar-type ATPase. These studies seek to understand the pathway of protons generated by calcification within the coccolith vesicle and the role of the V-type ATPase in calcification.

Calcium fluxes. The coccolithophorid cell is a fairly typical eukaryote living atypically in a 10 mM Ca2+ medium. Moreover, the cell mineralizes at the rate of some 40 picograms per light period. How does the cell control levels of calcium in the cytosol? How does it deliver calcium to the calcifying vesicle? How did this group of organisms uniquely evolve subcellular calcification? We are intrigued by many other similar questions.

Crystal nucleation and morphogenesis. We have a continuing interest in this topic and are collaborating with Betsy Read and Tom Wahlund at CSU San Marcos toward development of genetic and molecular tools for use on Pleurochrysis and Emiliania.

Prospective graduate students are encouraged to correspond either by letter, phone or email. Individuals who are interested in using molecular and biochemical tools to address ecophysiological problems of the coccolithophores are particularly encouraged to apply.